Self-staking insert

ABSTRACT

A SELF-STAKING INSERT HAVING A POLYGONAL SHANK WHEREIN THE SIDES ARE PLANAR AND ADJACENT SIDES OF THE POLYGON ARE JOINED BY ARCUATELY CURVED SURFACES SO AS TO PROVIDE A CONTINUOUS PERIPHERAL SURFACE WHICH APPROACHES CIRCULARITY, A BULGE PORTION AT THE LEADING END OF THE SHANK WHICH IS WIDER THAN THE RECEIVING HOLE IF PREPUNCHED AND WHICH TAPERS TO A CIRCULAR END FACE.

June 22, 1971 A. R. BREED ETAL Re. 21,143

' SELF-STAKING INSERT Original Filed Feb. 10, 1966 MM '1: II

v IIIIIIIIIII Iii-M: 36

FIG?

INVENTORS ARTH R. BREED EDW A, ANDERSON WM QM ATTORNEYS United StatesPatent 27,143 SELF-STAKING INSERT Arthur R. Breed, Euclid, Ohio, andEdward A. Anderson, deceased, late of Cleveland Heights, Ohio, byPhyllis T. Anderson, legal representative, Cleveland Heights, Ohio,assignors to The Lamson & Sessions Co., Cleveland, Ohio Original No.3,399,705, dated Sept. 3, 1968, Ser. No. 526,604, Feb. 10, 1966.Application for reissue July 30, 1969, Ser. No. 862,984

Int. Cl. F16b 39/00 US. Cl. 151-41.73 14 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE A self-staking insert having a polygonalshank wherein the sides are planar and adjacent sides of the polygon arejoined by arcuately curved surfaces so as to provide a continuousperipheral surface which approaches circularity, a bulge portion at theleading end of the shank which is wider than the receiving hole ifprepunched and which tapers to a circular end face.

The present invention relates to a metal insert for sheet or platemembers and more particularly to a self-staking type of insert.

In the type of insert to which the present invention relates, a portionof the insert is received in an opening in the plate or sheet member andanother part of the insert indents the sheet or plate member to causematerial to flow around the first part to securely hold the insertagainst both removal and rotation. Certain structures of the prior arthave utilized inserts with sharp edged grooves or knurls which bite intothe material of the sheet or plate member for holding the insert againstremoval and rotation relative to the member. Such sharp edged structurescause stress concentrations in the sheet or plate which cause earlypropagation of fatigue cracks when the plate or sheet member isdynamically loaded. Moreover, the structures have not been adapted foruse as punches and have not provided a noncircular body configurationwhere metal is flowed into substantially full circumferential contactwith the body.

An object of the present invention is to provide a new and improvedinsert such as an internally threaded fastener of the self-staking typewhich may be used with a prepunched hole or to punch its own receivingopening in a plate or sheet member and which, when inserted, is heldagainst rotation in the sheet or plate member, the insert being soconstructed and arranged that stress concentrations in the plate orsheet member are kept to a minimum thus providing a strong assemblyhaving a high fatigue life capability.

A further object of the present invention is to provide a new andimproved metal insert, such as an internally threaded fastener, of theself-staking type for assembly into a sheet or plate member, the inserthaving a central projecting portion of polygonal configuration and ahead portion for flowing the metal of the sheet or plate member intocontact, preferably full circumferential contact, with the polygonalcentral portion as the insert is assembled to the member with the insertbeing such that it is securely held against rotation and stressconcentrations in the sheet or plate member are minimized thus providinga strong assembly having a high fatigue life capability.

A further object of the present invention is to provide a new andimproved insert having a projecting central portion adapted to beinserted into a prepunched hole in a sheet or plate member for receivingthe insert or to punch a receiving opening in the sheet or plate memberin cooperation with a conventional die with the insert being soconstructed and arranged that maximum strength for punching purposes isobtainable in the projecting portion and the insert is securely heldagainst rotation while the stress concentrations in the final assemblyare held to a minimum.

A further object of the present invention is to provide a new andimproved insert of the self-staking type in which a central projectingportion has a polygonal shape with the shape approaching that of acircle to provide maximum punching strength and to avoid setting upunnecessary stress concentrations and yet having suificient angularitybetween the sides to securely hold the insert against rotation in aplate or sheet member.

A further object of the present invention is to provide a new andimproved self-stacking insert, such as an internally threaded fastener,which has a projecting portion adapted to be received in a prepunchedhole of a nominal diameter in a parent member to which it is to beassembled or to be used as a punch for punching a receiving opening incooperation with a standard circular die, the insert being soconstructed and arranged that the projecting portion will hold theinsert against rotation when inserted into a sheet or plate member withor without a prepunched hole and so that maximum strength can beobtained in the projecting portion.

Further objects and advantages of the present invention will be apparentfrom the following description thereof made with reference to theaccompanying drawings form-- FIG. 4 is an elevational view with parts insection showing a nut embodying the present invention to prepunch itsreceiving opening in a parent member;

FIG. 5 is a cross-sectional view of tooling for cold forming the nutblank for the nut shown in FIG. 1;

FIGS. 6 and 7 illustrate upsetting operations during the manufacture ofthe nut in FIG. 1; and

FIG. 8 is an elevational view of a modified form of a self-staking nutembodying the present invention with parts in section.

Referring to the drawings, the insert shown therein is a self-stakingnut 10 having a head portion 12 and a central projection 13 adapted tobe received in a prepunched opening or in a self-punched opening in asheet or plate member into which the nut is to be attached. The headportion 12 extends laterally outwardly of the projection 13 at one endof the nut and a tapped opening 14 eX- tends axially through the headportion 12 and the central projection 13. conventionally, the outer sideof the head portion 12 of the nut is considered the top of the nut.

The central projection 13 of the nut has a shank portion 13a which joinsthe head portion 12. The shank portion 13a, in cross section, has apolygonal configuration providing a continuous peripheral surface whichis adapted to hold the nut against rotation when the nut is insertedinto a plate or sheet member. In the illustrated and preferredembodiment, the polygonal configuration is that of a regular polygonhaving included angles between adjacent sides which are obtuse. In thepreferred Reissuecl June 22, 1971 3 practice of the present invention,the regular polygon is such that a circle inscribing the polygon has adiameter no smaller than 80% of the diameter of the circlecircumscribing the polygon and the diameter is no greater than thatwhich will provide a three-thousandths inch clearance as a minimumbetween a side of the polygon and the circle circumscribing the polygon.The included angle between adjacent sides of the polygon may be as smallas about 100 but preferably the shank portion 13a is at least hexagonalso that the included angle between adjacent sides is 120. It will benoted that in the type of regular polygon described, the sides of thepolygon form chords of the circle circumscribing the polygon. While thesides of the polygonal shank portion are planar, adjacent sides arejoined by arcuately curved surfaces which provide the aforementionedcontinuous peripheral surface. However, the self-staking nut could beconstructed, for example, by providing a continuous peripheral surfaceon the body thereof which is configured to provide a sinusoidalperiphery. The peripheral surface is termed continuous, since the shankportion is constructed so that there is no point on the periphery formedby the intersection of planar surfaces, that is, there are no portionsof the periphery formed by a line.

The lower end of the polygonal shank portion 13a flares out outwardlyand blends with a bulge portion 18 on the central projection. Thepolygonal sides of the shank portion 13a preferably extend along thebulge portion 18 to a point at which the diametrical extent of the bulgeis maximum. The bulge 18 therefore has the same general cross-sectionalconfiguration as the shank portion 13a. The central projection tapersfrom the bulge portion 18 to the outer end face 20 of the projection.The outer end face of the projection 13 is preferably more circular thanthe polygonal part of the projection and in the preferred andillustrated embodiment the portion of the projection immediatelyadjacent the outer end is generally frusto-conical in configuration andtapers outwardly to the maximum transverse dimension of the projectionat the bulge 18. The taper of the fruSto-conical portion, designated bythe reference numeral 21, preferably extends at a maximum angle of aboutwith respect to the axis of the tapped opening. It will be noted thatthe tapered portion extends higher at the corners of the polygon than atthe flats.

The underside of the head portion 12 includes a planar circumferentiallycontinuous surface engageable with the plate or sheet member as the nutis inserted therein to effect flowing of the material of the plate orsheet into engagement with the periphery of the projection 13. In thepreferred embodiment the underside of the head portion 12 is providedwith an annular recess 22 immediately adjacent the central projection 13which defines an indenting flange 23 having an annular surface 23aimmediately outwardly of the recess 22. The recess 22 opens downwardlyand the bottom thereof curves upwardly away from the annular surface 23aand then downwardly to blend with the central projection. The radius ofcurvature of the bottom of the curved recess is smaller immediatelyadjacent the projection and becomes progressively larger to provide aside surface 24 on the indenting flange which extends inwardly from theannular surface 23a and which is inclined to face toward the centralprojection 13.

The central projection 13 is designed so that the maximum transversedimension of the polygonal shank portion 13 is approximately the same oreven somewhat larger than the maximum transverse dimension of the outerend face 20. The outer end face is, as mentioned above, dimensioned suchthat it will fit into a prepunched hole with which the nut is designedto be used and is preferably substantially circular. As the nut isinserted into a prepunched hole, as is shown in FIG. 1, thefrustoconical portion 21 will cause the material of the parent member tocompress to allow the bulge 18 to pass through the material and theindenting flange 23 of the head portion will engage and indent thematerial of the sheet or plate member M to cause the material to flowaround the polygonal shank portion of the nut.

The recess 22 causes the indenting forces to be concentrated at theannular bearing surface 23a on the indenting flange and this surface isdesigned to have an area such that the normal punching pressure willovercome the yield resistance of the material to permit the indentingflange 23 to indent itself intothe material and to flow the materiallaterally to fiow around and engage the polygonal projection 13 forsubstantially the entire circumferential extent thereof. The inclinedsurface 24 of the indenting flange 23 will aid in directing the flow ofmaterial inwardly against the polygonal portion.

It will be noted that the annular surface 23a is, in the preferredembodiment, a continuous surface and therefore when the indenting flangeis indented into the sheet or plate member, it not only causes a flowinto engagement with the projection for substantially the entirecircumferential extent of the projection but it does not tend to set upundesirable stress concentrations in the receiving member. Moreover, thenature of the polygonal central projection 13 is such that the adjacentsides do not define sharp corners which tend to set up stressconcentrations. The included angles between the sides of the centralprojection 13 are obtuse angles which tend to minimize stressconcentrations. While the central projection preferably approachescircularity, the angle between adjacent sides is such that theprojection will securely hold the nut against rotation in the sheet orplate member.

The length of the projection 13 is such that the end face 20 ispreferably flush with or within the sheet or plate member when the nutis inserted into the member as is shown in FIG. 3. During insertion, thenut is backed by an anvil 26 or die member.

A self-staking nut embodying the present invention may be modified foruse with the parent member having a counter-sunk receiving opening. Sucha modified nut is illustrated in FIG. 8. The nut 10' comprises a headportion having an indenting flange 23' which is formed to ermit the nut,in its assembled condition, to be flush with the surface of a sheet orplate member having a prepunched counter-sunk receiving opening. Theindenting flange 23 includes a continuous annular bearing surface 23aextending between the projection 13 and an upwardly divergingfrusto-conical surface 23b which is formed to correspond with thefrusto-conical countersunk receiving opening in the parent member. Thebearing surface 23a provides a controlled indenting area such that asthe nut is advanced into the receiving opening the bearing surface willengage and indent the frustoconical wall of the counter-sunk opening toflow the material of the parent member into engagement with theperiphery of the projection 13'. The projection 13' of the nut 10 is ofthe same construction as the projection 13 of the nut 10, previouslydescribed.

Conventional dies and punches are commonly used to prepunch openings insheet metal or plate members for receiving the nuts. Rather than using apunch to prepunch a receiving hole, the nut itself may be used with theconventional punch die to punch the receiving opening for the nut as isiluustrated in FIG. 4. The punch die will have a nominal openingapproximately the same as the nominal opening of the opening to bepunched and the outer end face 20 of the polygonal projection 13 isdesigned to cooperate as a punch with the punch die.

As stated above, the outer end portion of the central projection ispreferably more circular than the polygonal shank portion and thecircularity is such that the clearance between the outer end of theprojection and circular die is preferably not more than 10% of thethickness of the sheet material to assure clean punching. It will beunderstood that the projection 13 is not actually received in the dieduring punching since it does not project outwardly of the plate orsheet member. The clearance specified however is lateral clearance whichwould be present if the outer end of projection were disposed at theouter end of the opening in the punch die.

By providing the described polygonal configuration on the shank portionof the projection 13, maximum strength is obtained in the projection 13for acting as a punch in cooperation with the punch die even though theshank portion is used to hold the insert against rotation. This enablesnuts or other inserts embodying the present invention to be used topunch receiving openings in materials of considerable greater thicknessthan heretofore possible.

To provide maximum strength in the nut, the nut is preferably a coldforged nut. One of the problems confronting the industry in forming acold forged nut as described is the problem of providing both the headportion and the bulge 18.

It has been found that the nut may be formed by first cold forging ametal slug in a die cavity to form a blank 29 with the general exteriorconfiguration of the nut without the bulge 18 but with an axiallyextending skirt 32 which is polygonal in configuration to correspond tothe shank portion.

Referring to FIG. 5, a die cavity 30 illustrated which has aconfiguration for forming, in cooperation with a punch 31, a blank 32having the exterior configuration of the nut without the bulge 18. Thedie cavity has a poly onal recess 33 in the bottom of the die cavity andforming an extension of the sides of the cavity for forming the axiallyextending polygonal skirt 32a about the periphery of the outer end ofthe central projection of the nut blank which is to be upset to form thebulge 18. As illustrated in FIG. 5, the punch member in cooperation witha projection in the die cavity also forms the central opening throughthe blank except for a web portion 35.

The blank formed in the die cavity 30' is removed from the die cavity30' by moving the blank axially out of the cavity and the web portionmay then be removed by a suitable punching operation. After the webportion is removed, the skirt is unset with an upsetting member 36 whichis moved against the end of the blank while the sides of the blank aresubstantially unrestrained. The upsetting member is illustrated in FIG.6 and has a flanged portion defining the 15 taper to control the flow ofthe material in the skirt to form the bulge. Initial attempts inupsetting the entire end of the blank to provide a bulge did not providea satisfactory bulging Without a distortion of the axial opening butwhen the circumferential skirt was provided adjacent the outer peripheryof the outer end of the central projection 13 and this skirt upset withan upsetting member having a wall defining thefrustoconical portion 21,it was found that a high satisfactory bulge was formed withoutdistorting the axial opening.

Having described our invention, we claim:

1. An insert adapted to be disposed in a hole in a plate or sheet memberwhich is prepunched and of given diameter [and] or which is adapted topunch a receiving hole during insertion in a metal plate or sheet membercomprising a body having a head portion and a central projection to bereceived in the hole extending outwardly from the head portion, saidhead portion extending laterally from said central projection and saidcentral projection comprising a shank portion having major and minordiameters, said minor diameter having a diametrical extent which is atleast 80 percent of said major diameter and the radial distance betweensaid diameters being no less than about 0.003 inch, said shank having anoncircular continuous peripheral surface with adjacent portions of saidsurface having high and low parts corresponding with said major andminor diameters respectively, said projection flaring laterally to abulge portion remote from said head and of a greater transversedimension than said shank portion, said shank portion being ofsubstantially uniform cross-section throughout its length with theconfiguration of said noncircular peripheral surface being discontinuousin an axial direction at said bulge portion and said bulge portionhaving a maximum transverse dimension larger than said given diameterand a tapering portion tapering inwardly in a uniform manner from saidbulge portion toward an outer end face of said projection, said taperingportion being approximately circular adjacent to the end thereof closerto the outer end face of said projection and tapering at an angle about15 degrees with respect to a longitudinal axis of said projection, [andmeans on] said head portion [outwardly of said projection for indentingthe metal of a plate member and effecting] being adapted to efiect aflow of the material of said member inwardly around said shank portion.

2. An insert adapted to be disposed in a hole in a metal plate or asheet member which is prepunched and of a given diameter [and] or whichis adapted to punch a receiving hole during insertion into a metal plateor sheet member comprising a body having a head portion and a centralprojection to be received in the hole extending outwardly from the headportion, said head portion extending laterally of said centralprojection and said central projection comprising a shank portion havingmajor and minor diameters, said minor diameter having a diametricalextent which is at least percent of said major diameter and the radialdistance between said diameters being, no less than about 0.003 inch,said shank having a noncircular continuous peripheral surface withadjacent portions of said surface having high and low parts of differentradius in cross-section and with the angle between any high part and anadjacent low part being no less than about 55 degrees with respect to aradius of said diameters through the high part, a bulge portion on saidcentral projection [at an end thereof] remote from said head of greatertransverse dimension than said shank portion and of greater transversedimension than said given diameter, and a tapering portion taperinginwardly from the bulge portion toward an outer end face of theprojection, said tapering portion being approximately circular adjacentto the end thereof closer to the outer end face, [and means on] saidhead portion [outwardly of said projection for effecting] being adaptedto efiect a flow of the material of a plate or sheet member inwardlyaround said shank portion the outer end of said projection having amaximum transverse dimension approximately equal to said major diameterand being received in a hole of said given diameter].

3. An insert as defined by claim 2 wherein said tapering portion tapersat an angle which is no more than about 15 degrees with respect to thelongitudinal axis of said insert.

4. An insert as defined in claim 2 wherein the configuration of saidshank portion is substantially polygonal with adjacent sides of thepolygon joining to form in wardly facing angles of less than degrees.

5. An insert adapted to be disposed in a hole in a metal plate or sheetmember which is pre-punched and of a given diameter [and] or which isadapted to punch a receiving opening on insertion into a metal plate orsheet member comprising a body having a head portion and a centralprojection to be received in the hole extending outwardly from the headportion, said head portion extending laterally of said centralprojection and said central projection comprising a substantiallypolygonal shank portion adjacent said head having a bulge portion [atthe end] remote from said head head of greater transverse di mensionthan said shank portion and of a transverse dimension greater than saidgiven diameter, said polygonal shank portion having a continuousperipheral surface with a minor diameter which is at least 80 percent ofits major diameter with the configuration of said noncircular peripheralsurface being discontinuous in an axial direction at said bulge portion,and a tapering portion tapering inwardly from the bulge portion towardan outer end face of the projection, said tapering portion beingapproximately circular adjacent to the end thereof closer to the outerend face, {and means on] said head portion [outwardly of said projectionfor indenting the metal of the plate member and effecting] being adaptedto eflect a flow of the metal inwardly around said shank portion[, theouter end of said projection having a maximum transverse dimensionapproximately equal to said diameter and being receivable in a hole ofsaid diameter].

6. An insert as defined in claim wherein said tapering portion tapers atan angle which is no more than degrees with respect to the longitudinalaxis of said insert.

7. An insert as defined in claim 5 wherein said projection isapproximately round at the outer end face of said projection.

8. An insert as defined in claim 5 wherein said polygonal shank portionhas a maximum transverse dimension approximately equal to the maximumtransverse dimension of the outward face of said projection.

9. An insert as defined in claim 5 wherein said projection isapproximately round at the outer end face of said projection.

10. An insert as defined in claim 5 wherein the insert is a cold forgednut.

11. An insert adapted tobe disposed in a hole in a metal plate or sheetmember which is pre-punched and of a given diameter and which is adaptedto punch a receiving opening on insertion into a metal plate or sheetmember comprising a body having a head portion and a central projectionto be received in the hole extending outwardly from the 'head portion,said head portion extending laterally of said central projection andsaid central projection comprising a substantially polygonal shankportion adjacent said head having a bulge portion at the end remote fromsaid head of greater transverse dimension than said shank portion and ofa transverse dimension greater than said given diameter, said polygonalshank portion having a continuous peripheral surface with a minordiameter which is at least 80 percent of its major diameter with theconfiguration of said noncircular peripheral surface being discontinuousin an axial direction at said bulge portion, and a tapering portiontapering inwardly from the bulge portion toward an outer end face of theprojection, said tapering portion being approximately circular adjacentthe outer end face and means on said head portion outwardly of saidprojection for indenting the metal of the plate member and efiecting aflow of the metal inwardly around said shank portion, the outer end ofsaid projection having a maximum transverse dimension approximatelyequal to said diameter and being receivable in a hole of said diameter,and wherein said tapering portion tapers at an angle which is no morethan 15 degrees with respect to the longitudinal axis of said insert,and [An insert as defined in claim 5] wherein said means on said headcomprises an axially extending flange having a substantially continuousbearing surface for engaging the metal plate or sheet to indent thelatter and a side surface facing said polygonal shank portion fordirecting metal inwardly against said shank portion for substantiallythe complete circumferential extent thereof adjacent said head portion.

12. An insert as defined in claim 11 wherein said projection isapproximately round at the outer end face of said projection.

13. An insert as defined in claim 11 wherein said tapering portiontapers at an angle which is no more than 15 degrees with respect to theaxis of said opening.

14. An insert as defined in claim 13 wherein said projection isapproximately round at the outer end face of said projection.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 2,008,229 7/1935 Sharp 151-41.73 2,490,594 12/1949Madden 15141.73 2,722,259 11/1955 Eckenbeck et al. 151-4173 3,117,6111/1964 Matthews 1514l.73 3,171,196 3/1965 Helitas 29 520 3,240,1003/1966 Rose 10 FOREIGN PATENTS 690,252 4/1953 Great Britain 15141.72947,097 1/ 1964 Great Britain 15141.73 955,813 4/ 1964 Great Britain24432 987,578 3/1965 Great Britain 15141.73 1,076,611 4/1954 France15141.73 1,091,566 10/1954 France 15141.73 1,300,424 6/1962 France15141.73

MARION PARSONS, 11L, Primary Examiner US. Cl. X.R. 2.9-432

